Method, system and apparatus for highly controlled light distribution from light fixture using multiple light sources (LEDS)

Info

Patent number: 8356916
Type: Grant
Filed: May 15, 2009
Date of Patent: Jan 22, 2013
Patent Publication Number: 20090323330
Assignee: Musco Corporation (Oskaloosa, IA)
Inventors: Myron Gordin (Oskaloosa, IA), Lawrence H. Boxler (Oskaloosa, IA), Garrett J. Young (Sully, IA), Matthew D. Drost (Oskaloosa, IA), Luke C. McKee (Oskaloosa, IA)
Primary Examiner: Laura Tso
Application Number: 12/467,160

Abstract

An apparatus, method, or system of lighting units comprising a plurality of lighting elements, such as one or more LEDs, each element having an associated optic which is individually positionable. In embodiments of the present invention, one or more optics are developed using optimization techniques that allow for lighting different target areas in an effective manner by rotating or otherwise positioning the reflectors, refractive lenses, TIR lenses, or other lens types to create a composite beam. The apparatus, method, or system of lighting herein makes it possible to widely vary the types of beams from an available fixture using a small number of inventoried optics and fixtures. In some cases, by using a combination of individual beam patterns, a small set of individual optics would be sufficient to create a majority of the typical and specialized composite beams needed to meet the needs of most lighting projects and target areas.

Description

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 of provisional U.S. applications 61/054,089 filed May 16, 2008 and 61/097,483 filed Sep. 16, 2008, which applications are hereby incorporated by reference in their entireties.

I. BACKGROUND OF INVENTION

Embodiments of the present invention generally relate to systems and methods for lighting. In particular, embodiments of the present invention relate to systems, methods, and apparatus for highly controlled light distribution from a light fixture using multiple light sources, such as LEDs (light emitting diodes).

Existing HID fixtures use single large light sources which provide light beams which can be controlled somewhat by varying reflector design and mounting orientation. Typical LED fixtures having multiple small light sources function similarly. Each small light source has an optic (reflective or refractive lens) which creates a particular beam pattern. The beams from each LED are identical in size, shape, and cover the same area (the offset of a few inches based on position within the fixture is insignificant given the size of the beam as projected). This means that the beam from the fixture is simply a brighter version of a single beam.

This approach requires the optic being used with the LED be designed to produce the final shape of the luminaire output (for example an IES type II distribution) when combined with the LED. The disadvantage of this approach is that the designed optic can only be used for one type of distribution and requires separate development, tooling, and inventory control for each optic and beam type. An example of these types of fixtures are the LED fixtures produced by BetaLED (Beta Lighting Inc., Sturtevant, Wis.; www.betaled.com) which use an array of identical “Nanoptic”™ lens which are designed for each different type of beam desired.

Thus, these fixtures may be improved with regard to controlling the distribution and intensity of the beam, and control of glare and spill light. A light fixture which provides a beam pattern that is more easily varied and controlled is therefore useful and desirable in the lighting industry.

II. SUMMARY OF THE INVENTION

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent, however, to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.

Embodiments of the present invention are described with reference to LEDs, LED lighting, etc., however, embodiments of the present invention are equally applicable to various other solid state (also referred to as solid-state) or other lighting devices (such as e.g., lasers) or fixtures that allow for multiple light sources to be packaged together in a small area.

For purposes of description it is convenient to describe the embodiments wherein the LEDs are facing up. For purposes of description of the composite beam output, it is convenient to describe the apparatus wherein the LEDs are facing down. Descriptions in terms of directional orientation is not intended to preclude mounting in any other orientation as desired.

It is therefore a principle object, feature, advantage, or aspect of the present invention to improve over the state of the art.

It is a further object, feature, advantage, or aspect of the present invention to solve problems and deficiencies in the state of the art.

Further objects, features, advantages, or aspects of the present invention include a method for creating a system of light distribution to provide lighting of a specified illumination to a pre-determined area. Said area can include standard beam shapes such as IES/NEMA beam types as well as individually customized beam shapes, including shapes having uneven light distribution with added or subtracted amounts of light in small areas which can be on the order of one meter square. One example, the composite beam, e.g. beam 200 as seen in simplified form from above in FIG. 2A, can be comprised of light beams 210 from a single fixture 10. Alternatively, the composite beam 220 may be formed from light beams 210 from multiple fixtures 10 that are part of a collective group (as seen in FIG. 2B). IES or IESNA (Illuminating Engineering Society of North America) and NEMA (National Electrical Manufacturers Association), and standard beam shapes are well-known to those skilled in the art.

Advantages of some embodiments include the ability to provide illumination of the desired shape, size and intensity to target areas of a pre-determined specification, such as corners, walkways, building surfaces, as well as areas in proximity to “low light zones” such as residences, parks, etc., using relatively high intensity (high candela produced), high efficiency (high lumens/watt) light sources. Other advantages include the ability to provide an even illumination of a target area that avoids harsh spots, shadows, glare, and other undesirable effects.

Further objects, features, advantages, or aspects of the present invention include an apparatus, method, or system of lighting units comprising a plurality of lighting elements, such as one or more LEDs, each element having an associated optic which is individually positionable. In embodiments of the present invention, one or more optics are developed using optimization techniques that allow for lighting different target areas in an effective manner by rotating or otherwise positioning the optics to create a composite beam. Associated optics may include reflectors, refractive lenses, TIR lenses, or other lens types. The determination of which type of associated optics to use can be based on applicability to a particular use such as emittance angle from the fixture, or manufacturing costs and preferences, for example.

Further objects, features, advantages, or aspects of the present invention include an apparatus, method, or system of lighting which makes it possible to widely vary the types of beams from an available fixture using a small number of inventoried optics and fixtures, thereby potentially reducing fixture cost, reducing lead time for custom lighting, and multiplying the versatility of any new fixtures or optics which could be created. In some cases, by using a combination of individual beam patterns, a small set of individual optics (perhaps on the order of less than 10) would be sufficient to create a majority of the typical and specialized composite beams needed to meet the needs of most lighting projects and target areas.

Apparatus

Some embodiments of the present invention provide for an apparatus comprising a lighting fixture with a plurality of individual light sources. The plurality of individual light sources may include solid-state light sources (such as LEDs). Each light source may include its own optic with elements such as reflectors, refractive lenses, light blocking tabs, and/or other elements. Each individual optic, according to embodiments of the present invention, is part of an array of optics placed in a specific location relative to the fixture and/or the other light sources. This array could be an arrangement of rows, a circular, radial, spiral pattern or any other pattern or shape. The individual optics could be mounted in the fixture by a means that also provides for adjustment in one or more directions relative to the light sources so as to vary the location of the individual beam within the composite beam. Adjustment of the optics could be preset by the manufacturing or assembly process, or the fixture could be manufactured such that the rotational position of individual optics could be set at installation or at a later time. This could allow, for example, a local inventory of individual fixtures that could be very quickly configured for given applications.

While traditional LED fixtures commonly mount the LEDs with snap-fit components and/or adhesives, these mounting techniques can lead to loss of position or alignment, or fixture failure within a short period of time relative to desired lifetime of area lighting fixtures (i.e., a few years vs. a desired lifetime on the order of decades). The envisioned mounting/adjustment method and apparatus provide improvements in the art.

According to embodiments of the present invention, the fixture may include LEDs mounted on a substrate that may be a circuit board of laminated or layered metal, standard circuit board materials and/or other materials that provide dimensional stability, a means to provide or affix necessary circuitry, and optional benefits for thermal management.

In embodiments of the present invention, the fixture may optionally include elements to further direct or control the individual beams such as tabs (e.g. 35, FIG. 9,) or analogous structure which may be affixed within the fixture relative to one or more individual light sources and placed in such a way as to restrict direct, non-reflected or non-controlled light or similarly to restrict light emitted at an angle which is not desired for the particular application.

System

Embodiments of the present invention provide for a system that uses a plurality of fixtures or fixture groups placed at various spaced-apart locations within or around an area to be lighted. Further, embodiments of the present invention can use one or more groups with one or more fixtures per group to provide a desired level of illumination within a target area of a pre-determined specification in order to provide coordinated benefits of the above lighting method for areas such as sports fields, parking lots, buildings, etc.

Method of Designing Lighting System

According to embodiments of the present invention, designing the lighting system may require two or three separate steps, including analyzing the intended application, selecting individual optics, and designing the composite beam. These steps may be repeated as necessary to optimize the design.

a) Creating Composite Beam

In one aspect, the beam is composed as follows: the light beam from each optic (i.e. the beam produce by light from a light source which is directed by the optic) produces a portion of the overall beam pattern. This beam portion may be the primary or essentially the only light source for a certain portion of the target; alternatively, by combining a set of these optics that project various beam types (for instance circular, elongated, or oblong beams), a series of overlapping beams can be built to a desired pattern (e.g. FIG. 3D) at a desired level of illumination, which can help to compensate for the distance (inverse square law) and incident angle (cosine law) or for other factors. For example, more individual beams can be directed towards the farther edges of the composite beam (see e.g. FIG. 3B), or different beam patterns (e.g. circular, elongated, narrow, wide, etc.) having different intensities can be created such that distribution in the target area is even (e.g. many ‘ten degree’ circular beams might be used for illuminating the area farthest from the fixture, while fewer ‘twenty degree’ beams could be used closer to the fixture and so on). The beam edges may overlap the adjoining beam at any desired degree to provide uniform distribution or the entire beam may overlap another beam to increase the intensity, and the composite beam can be composed of a combination of a number of individual beams of different sizes, shapes, distribution angles, and orientations (e.g. subject only to available lens design, an “oblong” beam 403 FIG. 4 could be oriented axially with the beam, transverse to the beam, or at some other angular orientation relative to the beam axis). The result would be a beam distribution, in a rectangle, oblong, oval, circle, fan, or other shape as desired as illustrated in FIGS. 3A-3E.

In accordance with embodiments, as might be used on a sports field, such a beam could provide illumination at, for example, the base of the light fixture mounting pole as well as to distant areas on a field. Additionally, in embodiments of the present invention, the beam could be cut off at the edge of a field (FIG. 3C) while still providing adequate illumination close to the edge of the field. Examples of shapes which can be easily adapted to illuminate, for example, the corner of a field (FIG. 3E), a football field (see FIG. 3D), a short and wide building 270 (see FIGS. 14A-C), a tall and narrow building 280 (see FIGS. 15A-15B), as well as many other specific shapes and configurations are shown.

‘Pixellation’

Unlike conventional lighting fixtures, embodiments of the present invention can provide ‘granular’ or ‘pixellated’ control of light at a high level of precision, wherein for a given application, small areas, which could be on the order of 1 square meter (more or less according to lens design, mounting height, fixture mounting angle, etc.), can have brightness somewhat controlled. This allows areas within the target area to be emphasized. For buildings, signs, or other applications where a sharply defined shape is to be illuminated, these embodiments provide greater flexibility than conventional lighting.

In an example, an HID lamp putting out 36,000 lumens can cover approximately 180 m.sup.2 (an area 12 m.times.15 m) at 200 lux (lumens/m.sup.2). Embodiments of the present invention provide for a fixture that includes multiple LEDs that can cover the same 180 m.sup.2 area. Each single LED, in one example, is capable of putting out 200 lumens and provides enough light for one square meter. This provides a level of precise control that provides, in effect, a “pixel by pixel” control of illumination on a target area, which both conventional HID and LED lighting cannot do. Both conventional HID and conventional LED fixtures are limited to the beam pattern as projected from the fixture, with minor modification possible by use of methods which can only affect the whole beam or a large portion of the beam.

Additional Optional Elements

An embodiment that uses reflective-type lenses might not work well if a flat plate glass cover, e.g. 40, FIG. 1B, were required for the fixture and the fixture needed to be oriented more or less parallel to the ground, since some beam patterns might require a high angle of incidence. The result might be that the light might be reflected by the surface of the cover rather than transmitted through the cover. In this case, it might be more effective to use the refractive lens design or to change the cover design. Use of anti-reflective coatings for covers is well known in the art, with theoretical allowable angles of incidence up to 60° from normal, which could increase usability of refractive lenses at higher angles. However, their use is generally limited to about 45 degrees from normal, which could make the use of refractive lens arrays rather than reflective arrays more effective under some circumstances.

Optional additional elements could include an additional lens or lenses or other optical element in association with the fixture which may contribute to the overall lighting effect or may provide other benefits such as enhanced aesthetics, protection of the components of the fixture, or reducing any unpleasant visual effects of directly viewing the fixture.

A fixture using an array of LEDs could allow light at an angle which is relatively controlled and that might be acceptable for some applications but could still benefit from additional control. Using a single visor of a type which is common to existing lighting fixtures would tend to either completely block the light emitted from the lights near the front of the fixture (refer to FIG. 7B) or to have little or no effect on the angle of emission from the light sources near the rear of the fixture. (refer to FIG. 7C). Multiple visors 797 as shown in FIG. 7D would provide an additional novel means of precisely controlling light from a fixture.

Aimability

Some embodiments of the invention provide or enhance the ability to pre-aim a fixture at the factory relative to a particular location or application. The envisioned embodiments may be easily pre-aimed, since their placement of light on an area can be accurately established and indexed to the intended mounting positions of the fixtures. Additionally, the fixtures may be aimed precisely in the field by indexing from individually aimed lights/optics or from precision manufactured reference location on the fixture.

III. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments and aspects of the present invention will be described and explained through the use of the accompanying drawings in which:

FIGS. 1A-1B illustrate a fixture according to embodiments of the present invention;

FIG. 1C illustrates optics according to embodiments of the present invention;

FIG. 1D illustrates a substructure or frame which provides orientation and indexing according to embodiments of the present invention;

FIG. 1E illustrates a method of assembly of an array of LEDs and optics according to embodiments of the present invention;

FIGS. 2A-2B show aspects of formation of a composite beam according to embodiments of the present invention;

FIGS. 3A-3E illustrate potential composite beam layouts according to embodiments of the present invention;

FIG. 4 shows examples of some beam shapes that may be created or used as sub-beams according to embodiments of the present invention;

FIG. 5 illustrates aspects of an example fixture using reflector type optics according to embodiments of the present invention;

FIG. 6A shows Bezier controls used in the design of a reflective optic element according to embodiments of the present invention;

FIG. 6B is a graphical representation of an untrimmed image of an optic created according to embodiments of the present invention;

FIG. 6C is a graphical illustration of the trimmed image based on the trim line of an optic created according to embodiments of the present invention;

FIG. 6D shows isocandela traces based on a typical parabolic reflective optic element;

FIG. 6E shows footcandle traces based on a typical parabolic reflective optic element;

FIG. 6F shows isocandela traces based on a modified reflective optic element created according to embodiments of the present invention;

FIG. 6G shows footcandle traces based on a modified reflective optic element created according to embodiments of the present invention;

FIGS. 7A-7D illustrate the need for and application of a ‘visor’ according to embodiments of the present invention;

FIGS. 8A-8B illustrate an application of the ‘visor’ to arrays of LEDs according to embodiments of the present invention;

FIG. 8C illustrates a section view (with some lines removed) of a fixture according to embodiments of the present invention having ‘visors’ applied to arrays of LEDs according to embodiments of the present invention;

FIG. 9 illustrates an application of a reflective tab to an array of LEDs according to embodiments of the present invention;

FIG. 10 illustrates a means of adjustment of an optic according to embodiments of the present invention;

FIGS. 11A-11B illustrate differences in the effect of lighting with and without control of spill light;

FIGS. 12A-12C illustrate a composite beam with a relatively narrow beam and large incident angle according to embodiments of the present invention;

FIGS. 13A-13C illustrate a composite beam with a wide beam which projects light from a low to high range of incident angles according to embodiments of the present invention;

FIGS. 14A-14C illustrate another building type that might be illuminated by a fixture in accordance with embodiments of the present invention;

FIGS. 15A-15B illustrate how a fixture, in accordance with embodiments of the present invention can provide precise illumination on the face of a tall, narrow building. For comparison, a conventional fixture with a conventional round beam on a tall, narrow building is shown in FIG. 15C;

FIGS. 16A-D are similar to FIGS. 14A and B and showing how a beam that could be suitable for a wide building could be modified to be suitable for a narrow building.

The figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the drawings may be expanded or reduced to help improve the understanding of the embodiments of the present invention. Moreover, while the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the figures and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives.

IV. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of the present invention provide for an apparatus, system, and method tor creating a composite beam from LEDs (or other individual light sources) and associated optics such as reflectors or lenses. The composite beam can be comprised of light beams from a single fixture (see FIG. 2A), or light beams from light sources of multiple fixtures that are part of a collective group (see FIG. 2B). Said fixture contains a plurality, which may be a large plurality, of individual light sources 20, FIG. 1A and their associated optics. Associated optics may include reflectors 30, FIG. 1A, refractive lenses 60 FIG. 1C, TIR lenses 50 FIG. 1C, or other lens types. The determination of which type of associated optics elements to use can be based on applicability to a particular use, which can include considerations of type and shape of fixture (e.g. in order to consider such things as wind loading and aesthetics), mounting angle, ambient conditions, etc.

A. Exemplary Method for Designing a Lighting System—Overview

In general, the lighting professional using embodiments of the present invention will first analyze the intended application, then, select individual optics, and design the composite beam. Of course this process may be iterative given possible design conditions and constraints.

Analyzing the Application

In analyzing the application, a determination will be made regarding the size and shape of the intended target area and desired illumination level based on intended usage, yielding a total desired lumens value or figure. Then a determination of the minimum number of fixtures of the type anticipated to be used can be made, based on the number of lumens per light source and number of light sources per fixture which must provide the required total lumens. These values, parameters, or figures will then be modified, based on requirements for the target area, such as e.g. preferred, allowable, and prohibited fixture mounting locations, fixture setback from the target area, mounting height, calculations of angle of incidence of the illumination and consideration of the inverse square law of optics. Given these items, using one of several possible methods, the lighting designer will begin designing the light layout to provide desired illumination of the target area. This will be similar to designing using conventional HID or LED fixtures. However, the designer can plan lighting at a much finer scale since the individual light sources each contribute a small amount to the total light applied to the entire target area. Additionally, unlike using conventional HID or LED lighting, if there are any areas for which the amount of light should be increased or reduced, this can be accomplished by changing the aiming of a few individual light sources without necessitating a significant reduction or increase in light on adjacent areas.

a) Select or Design Individual Optic

If satisfactory individual optics for the given application are already in existence, one or more types may be selected to potentially meet the needs of the application which has been previously analyzed. If not available from previous design, new ones may be designed. One method that may be used according to embodiments of the present invention is discussed later.

One advantage of the present invention is that a single optic, or limited number of optics, can be used to create multiple lighting configurations. This is done by creating an optic that creates a portion of a beam pattern that can be used with an LED or similar light in an array of similar lights to create the desired final beam pattern shape from the luminaire (e.g. IES type V). The desired final beam pattern is created using the aforementioned designed optic with an LED array and positioning the optic at various angles to the LED to create the final beam pattern using the sub-pattern from each optic. FIG. 2A illustrates an example of a composite beam 200 formed by sub-beams 210.

While embodiments of the present invention can be used for creating area lights having patterns as prescribed by the IES types, the pattern from the luminaire is not constrained to the IES types and can be used to custom configure a luminaire for a specific lighting task.

Select or Design Fixtures

Within the design process, individual fixtures will be selected for use with the appropriate optics. These fixtures will be placed in groups on poles or in mounting locations according to the overall plan for the application. At this point the original design considerations and selection of optics will be re-examined and changes made as necessary to fine-tune the design.

B. Detailed Development of Optics

Deficiencies of Parabolic Optics

The development of the optic for the sub-beam is now described according to certain aspects of the invention. While a parabolic optic is easily designed and may be used in embodiments of the invention, other types of optics can provide more desirable results. It is well known that a parabolic surface when combined with a light source at the parabolic focus produces a spot beam that is aimed along the axis of the parabola. This spot beam can be directed by pointing the parabolic axis in the desired direction. However, one disadvantage of the spot beam from the parabola for area illumination is that the intensity profile from the reflector will create a non-uniform distribution on the area being illuminated, with an intense spot in the center with a sharp transition to zero light on the edge. This is ordinarily not a optimum output beam for use in illuminating areas. A desirable pattern usually contains a more uniform distribution with light directly below the luminaire smoothly transitioning to the edge of the beam.

Embodiments of the present invention provide for systems and methods for being able to develop several different beam types from a single optic design that has been specially designed to allow for the smooth blending of a sub-beam into a composite beam. This is accomplished with a single optic rather than multiple optics, a single development cycle, and a single piece to inventory, resulting in distinct advantages in cost and speed to market.

Embodiments of the present invention provide for creating a modified parabolic shape to produce an output beam that both projects a spot to be used as a sub-beam, and creates a smooth distribution on the area being illuminated in order to have sub-beams that can be combined to create desirable illumination beams from the full luminaire. An example angular output for a parabolic optic pointed at 70.degree. to nadir and a CREE (Durham, N.C. USA) model XRE White LED is shown in the graph in FIG. 6D (units are candela), which illustrates a characteristic “spot” type beam from the system. Taking this beam and using it to illuminate a plane 10 feet below the system as an area type light yields the distribution on the ground shown in FIG. 6E (units for the output are footcandles).

Modifying Parabolic Optics

An example starting point with Bezier control points 600 is shown in FIG. 6A. Each control point is parameterized via its X, Y, Z coordinate and its control point weight W. The basic parabola shape produces a spot beam.

The parabolic shape is parameterized using a Bezier polynomial scheme to allow for adjustment of several parameters to control the reflector shape to achieve a desired output distribution. Bezier mathematics are used extensively in computer aided design and are known to those skilled in the art. The result of using Bezier mathematics is a simplified list of points and control points that generally describe the surface and allow for manipulation of the surface through these parameters. The use of Bezier splines for optical design is well documented.

The parameterized parabola is redefined using an automated optimization routine to drive the reflector shape to produce a sub-beam that will produce a more uniform output beam when arranged as with the parabola spot beams above. The optimization routine is a genetic algorithm (see, e.g., Vose, Michael D (1999), The Simple Genetic Algorithm: Foundations and Theory, MIT Press, Cambridge, Mass. Whitley, D. (1994); and A Genetic Algorithm Tutorial. Statistics and Computing, 4, 65-85). A genetic algorithm can be beneficial in solving these types of problems due to the large number of variables and the uncertain behavior of the merit function. The genetic algorithm used may include real valued chromosomes along with tournament selection, crossover, and mutation. Other variations of genetic algorithms can be used as required. The merit function in at least one embodiment is defined as the falloff of illumination from the center of the pattern to the edge of the pattern. The value of the merit function was increased as this falloff became closer to a linear falloff. Of course, depending on the desired use, the merit function would be different for different applications. The merit function is well-known (see, e.g., Press, W. H.; Flannery, B. P.; Teukolsky, S. A.; and Vetterling, W. T. “Bessel Functions of Fractional Order, Airy Functions, Spherical Bessel Functions.” .sctn.6.7 in Numerical Recipes in FORTRAN: The Art of Scientific Computing, 2.sup.nd ed. Cambridge, England: Cambridge University Press, 1992).

Table 1.0 shows the surface definition of an optic that was created using this merit function. The optic is defined by the 3rd Degree X 3rd Degree Bezier Patch Description (see, e.g., U.S. Pat. No. 5,253,336 regarding 3^rdDegree Bezier Patch):

TABLE 1.0 Surface Definition Pt # X Y Z Weight 1 9.52 7.88 −0.79 1.000 2 11.59 6.18 5.97 1.547 3 7.82 4.74 13.22 2.368 4 6.84 −0.04 −0.46 1.296 5 9.70 1.83 3.48 2.968 6 5.43 3.48 10.46 3.859 7 3.61 −4.24 −0.15 0.739 8 5.28 −0.96 4.98 1.846 9 3.19 1.34 9.22 0.771 10 0.00 −2.63 0.00 1.000 11 0.00 −2.60 6.91 2.113 12 0.00 0.67 9.27 0.727 13 0.00 4.57 11.53 1.000

Note that only the right half control points are listed as the left half is symmetric about y axis. FIG. 6B is a graphical representation of the untrimmed image (showing control points on both halves), while FIG. 6C is a graphical illustration of the trimmed image based on the trim line described in Table 2.0.

TABLE 2.0 Trim Line for Notch Pt # X Y Z 1 0 0.54 0 2 0.213 0.54 0 3 2.647 4.645 0

After optimization of the shape, the sub-beam has the following angular and illumination outputs as shown in FIGS. 6F and 6G. When the optics are subsequently arranged by rotation around the LEDs to achieve a specific pattern, the resulting output pattern is a more desirable illumination.

Exemplary Genetic Programming Algorithm

In embodiments of the genetic algorithm, the variables that are manipulated are the X, Y, and Z coordinates of each control point, along with the Bezier Weight of each control point (see, e.g., Xiaogang Jin and Chiew-Lan Tai, Analytical methods for polynomial weighted convolution surfaces with various kernels, Computers & Graphics, Volume 26, Issue 3, June 2002, Pages 437-447). For the specific example, there were 36 variables. The merit function was determined by taking a slice through the illuminance data from a single reflector starting at 5 feet from the fixture out to 50 feet from the fixture. The data was taken in 1 foot increments, and then compared to a theoretical uniform line through those same points. The deviation from the line at each point was calculated and squared, and the total difference was the square root of the sum of those squares. The fitness function for the algorithm has to actually increase to show better performance, so the final merit value was I/(total difference) so that it would approach infinity as the fit to the line got better. The actual code to calculate the fitness is shown here:

M1=0 $DO 5 50 { VALUE ? 0 P1 M1=M1+((−0.0356*(?)+4.4778)−P1){circumflex over ( )}2 } RETURN LINEDIF=SQRT(M1) FITNESS=1/LINEDIF

In the specific example, a real valued chromosome was used (in other words, the Ivariables were not converted into zeros and ones) with 36 Genes (the total number of variables). The population size was set to 100. A tournament format was used to determine which chromosomes survived to be parents of the next generation and had 8 individuals compete in the tournament. The tournament selection was random. Crossover was performed using a random crossover mask where a 0 means to keep the first parents gene and 1 means to keep the second parents gene and reversed the order of parents to generate a pair of children for each pair of parents. Mutation in the children was allowed using a mutation threshold of 0.3 (30% chance of mutation) with a mutation amount limited to 37.5% (the amount of mutation was chosen randomly to be between 0 and 37.5% if mutation occurred). 1000 generations for the optimization were run.

As will be appreciated by those of ordinary skill in the art, there are probably other combinations that could be used to either speed up the results or obtain higher fitness functions.

C. Exemplary Method—Creating Customized (Non-Standard) Beam Shapes

Customized Beam Principles

In accordance with embodiments of the present invention, individual optics may be designed using well-known optical principles to project a beam of a desired shape and distribution. For example, the optic can provide a type 5 lateral beam distribution with long vertical distribution, or a type 2 lateral beam distribution with short vertical distribution, or any other desired beam distributions. Design and construction methods for the optical lens and reflector are well known in the art. Fixtures which are nearly parallel to the ground which are illuminating a distant target have an emittance angle that is ‘flatter’ relative to the fixture, for which reflective optics may be more appropriate, while fixtures which oriented more vertically relative to the ground, or which are illuminating a target that is less distant or that is directly underneath have an emittance angle that is ‘steeper’ relative to the fixture, for which refractive optics may be more appropriate. However, there is considerable overlap between the alternatives and therefore choice of reflective vs. refractive would be made according to the circumstances. Alternatively, for some applications, use of both reflective and refractive optics on the same fixture might be appropriate.

Design of Composite Beam per IESNA

Having analyzed the overall application of the light to the target area, and selected or designed the appropriate individual optics, the designer will lay out each individual optic within each fixture to design the composite beam. In order to design a specific composite beam for a given application and target area, several methods could be used which are known to those of ordinary skill in the art. A discussion of several methods can be found in the IESNA Lighting Education: Intermediate Level, New York: Illuminating Engineering Society of North America, © 1993, sections 150.5A and 150.5B.

In embodiments, light modeling can be used to select the optic design and orientation of the individual light beams to create the composite beam from the fixture. For example, selecting one or more of the beam shapes 400-403 shown in FIG. 4 or from other beam shapes, the lighting designer, with optional assistance from a commercially available lighting software program, can produce the desired composite beam shape and intensity. The designer can determine the number and combinations of beam patterns provided by the lenses within the fixtures. For each project, the designer can proceed to select individual fixtures which use a certain number of reflective and/or refractive lenses. As designed, the selected lenses would be assigned a position and orientation within the fixture such that light is distributed as desired on the target area. In accordance with embodiments of the present invention, special consideration can be given to edges of target areas in order to provide even lighting at the edges without excessive spill light beyond the target area.

Design of Beam By Luminaire Equivalence

Another method of designing a specific composite beam in embodiments of the present invention is calculating the “luminaire equivalence” of each individual optic combination, using existing or custom lighting design software. Using this method, each individual source is considered as a luminaire. The designer can select the optic system based on its photometric properties and place the light from each individual source onto the target area as desired. This process would be repeated until the desired composite beam shape and intensity level was achieved. In one or more embodiments, some level of automation could be added to the design process if desired.

Design of Beam by Standard Layout Tools

Another method of designing a specific composite beam in accordance with embodiments of the present invention is to use standard layout tools such as drafting board, computer-aided design software or other tool(s) to arrange the selected beam shapes to create a composite pattern. For example, if the composite beam pattern desired looked similar to as shown in FIG. 3B then the available optics would be selected based on their distribution and intensity. These individual beams would be arranged to fill the area and multiple beams overlaid to achieve the desired intensity.

The following Table 3.0 describes the optic selection and orientation of the individual beams form the light source optics system to create a composite beam shown in FIG. 3B.

TABLE 3.0 Reflector Rotation (0 degrees is straight Optic type out, 90 is left and (see FIG. 4) right) 400, 402 0 400, 402 7.5, −7.5 400, 402 15, −15 400, 402 22.5, −22.5 400, 402 30, −30 400, 402 37.5, −37.5 400, 402 45 400, 402 52.5 400, 402 60 400, 402 67.5, −67.5 400, 402 75, −75 400, 402 82.5, −82.5 400, 402 90, −90 401 −45 401 −52.5 401 −60

Design of Beam by Other Methods

Other methods of composite beam design are possible and considered included in this application.

In addition to designing a composite beam based on the use of a single fixture, embodiments of the present invention may use multiple fixtures to target the same or overlapping areas in order to build up intensity to desired levels based on well known principals of lighting. The composite beams from two or more fixtures would be combined to provide illumination over the entire target area.

Customized Beam Examples

The following figures illustrate various simplified composite beams in accordance with embodiments of the present invention. FIGS. 12A-C show a composite beam with a relatively narrow beam 240 and large incident angle. FIGS. 13A-C shows a composite beam 250 with a wide beam which projects light from a low to high range of incident angles. FIGS. 15A-B shows how a fixture of the type envisioned could provided precise illumination on the face of a tall narrow building. FIG. 15B illustrates a representation of how the individual beams might be combined to cover the desired areas on the building while essentially avoiding wasted or ‘spill’ light.

FIG. 15C shows a building as it might be illuminated by a conventional light fixture or an LED type fixture with simple optics. The rounded beam fully illuminates the building but has significant spill light 290. FIG. 15B shows, in simplified form, how the same building might be illuminated by the composite beam from a fixture in accordance with embodiments of the present invention. The multiple individual beams are directed so as to avoid significant spill light but to provide complete illumination of the target area.

FIGS. 14A-C illustrate another building type that might be illuminated by a fixture in accordance with embodiments of the present invention. FIGS. 16A-D show how an existing fixture that provides light beam 320 which is suitable for illuminating a wide building (300) spills over at 330 and would be unsuitable for a narrow building 310. The beam as modified (340, FIG. 16D) illustrates how fixture 10 could be designed to provide the correct illumination for building 310 in accordance with embodiments of the present invention.

The composite beams of FIGS. 3A-E also illustrates how customized, or non-standard, composite beam shapes can be created to fit the needs of special applications. For example, the composite beam of FIG. 3E would be well suited for illumination in the corner of a target area. FIG. 3B also illustrates how the intensity in the distal portion of the beam can be increased by overlaying beams, (beam shapes 400 and 401 in this example).

D. Exemplary Apparatus—Reflective Lens Fixture

Fixture Construction

One example of a fixture 10 with individual optics is shown in FIG. 1A. The solid-state light sources 20 are mounted on a circuit board 80, FIG. 1E, or other structure, in an offset row pattern. According to embodiments of the present invention, other patterns could also be used. Individual reflectors produce the desired beam pattern from each source and are also mounted on the circuit board, above each light source and oriented in the desired direction. The reflectors in embodiments of the present invention can be more or less specular, diffusing, and/or absorbing, depending on the desired effect.

Various methods of attaching the reflector to the circuit board, or other structure, are available in embodiments of the present invention. Examples of means for attaching the reflector include, but are not limited to, mounting as individual pieces above the light sources, mounting pins, fasteners or adhesive. An automated pick and place assembly machine can be used in embodiments of the present invention to ensure accurate placement of the reflectors and correct orientation per the lighting design. Alternatively, the reflectors can be mounted to a substructure or frame 90, FIGS. 1D-E, which provides orientation and indexing.

Optics

The individual optic used in the fixture of FIG. 1A is a reflector (30, FIG. 1C) over the LED light source 20 which projects the light in a desired pattern, based on the reflector design. The plurality of reflectors are oriented in various directions, providing a beam pattern as illustrated in FIG. 2A as one example of a possible composite beam pattern. Orientation of each reflector is determined based on the desired beam pattern and intensity.

The reflectors can be offset from each other to avoid potentially blocking light from the light source to its rear. They can include an optional v-shaped notch in reflector 30 (FIG. 6C and FIG. 9) to allow some of the light to be directed downward instead of outwardly. This provides lighting directly below or in front of the fixture. FIG. 5 illustrates an array 500 of individual light sources and examples of possible angular orientations for typical reflectors in accordance with embodiments of the present invention.

The reflector can be made of various materials depending on application, cost considerations, availability, etc. For example, a reflector could be made of molded plastic with metallized surface, injection molded, machined and polished from aluminum, etc.

An example of a type of adjustment or indexing method could be capturing the individual lenses in a circular hole which could have degree or index marks. The lenses could be equipped with a screwdriver slot and adjusted to a desired position. Or lenses could be positioned by precision equipment which is temporarily indexed to the fixture. Lenses might be held in place by a friction fit or by any number of clamping or fastening methods. The optics could also be simply positioned in a matrix 90, FIG. 1E, using an indexing system (e.g. cut-outs 95, spacers, bosses, etc.). Additionally, fine-tuning of light distribution could be accomplished on site, and light distribution from a fixture could be modified if needs for a specific location should change.

In accordance with some embodiments, the indexing system could be machined or manufactured automatically as part of the matrix 90; the array of optics can be attached such that the predetermined spacing, rotational positioning, etc. is established and maintained with reference to the individual light sources and the light fixture by using mounting pins, screws, bosses, etc. that mate precisely with indices in the mounting structure of the individual light sources (see e.g. 100, FIG. 1E). Further, this method of mounting could provide a high degree of accuracy in mounting over a long period of time (on the order of decades of years), and the method of mounting the optic array to the individual light sources relies on a small number of components manufactured to certain tolerances in order to ensure precise indexing of the mating components.

Further adjustments could be included as part of the system to allow adjustment in a plane that is not generally parallel to the fixture. For instance, reflectors could be adjusted by ‘tipping’ the reflector relative to the mounting plane, using trunnion-type mounts 55 with e.g. setscrew 45 or gear and sector adjustments (see FIG. 10). Similarly, overlays could be designed to hold the reflector at a specific ‘vertical’ angle relative to the mounting surface or template.

Example of Beam Layout

Table 4.0 describes one possible method of arranging the individual beams from the light source optics system in FIG. 5 to create a composite beam. In this example, the general composite beam is an IES type 4 shape. The reflectors in this embodiment are all parabolic but other shapes could be used. In this example, the general composite beam is produced with a common optic design, of a parabolic design, used throughout the set of light sources on the fixture 500. See FIG. 5 for an example fixture and optical layout in reference to Table 4.0 below.

TABLE 4.0 Reflector Rotation (0 degrees is straight Source/optic X Y Z out, 90 is left and ID # (mm) (mm) (mm) right) 1 0 0 0 −90 2 28 0 0 90 3 56 0 0 −90 4 84 0 0 90 5 112 0 0 −90 6 140 0 0 90 7 168 0 0 −90 8 196 0 0 90 9 224 0 0 −90 10 252 0 0 90 11 280 0 0 −90 12 308 0 0 90 13 336 0 0 −90 14 364 0 0 90 15 0 28 0 −82.8 16 28 28 0 82.8 17 56 28 0 −82.8 18 84 28 0 82.8 19 112 28 0 −82.8 20 140 28 0 82.8 21 168 28 0 −82.8 22 196 28 0 82.8 23 224 28 0 −82.8 24 252 28 0 82.8 25 280 28 0 −82.8 26 308 28 0 82.8 27 336 28 0 −82.8 28 364 28 0 82.8 29 0 56 0 −75.6 30 28 56 0 75.6 31 56 56 0 −75.6 32 84 56 0 75.6 33 112 56 0 −75.6 34 140 56 0 75.6 35 168 56 0 −75.6 36 196 56 0 75.6 37 224 56 0 −75.6 38 252 56 0 75.6 39 280 56 0 −75.6 40 308 56 0 75.6 41 336 56 0 −75.6 42 364 56 0 75.6 43 0 84 0 −68.4 44 28 84 0 68.4 45 56 84 0 −68.4 46 84 84 0 68.4 47 112 84 0 −68.4 48 140 84 0 68.4 49 168 84 0 −68.4 50 196 84 0 68.4 51 224 84 0 −68.4 52 252 84 0 68.4 53 280 84 0 −68.4 54 308 84 0 68.4 55 336 84 0 −68.4 56 364 84 0 68.4 57 0 112 0 −61.2 58 28 112 0 61.2 59 56 112 0 −61.2 60 84 112 0 61.2 61 112 112 0 −61.2 62 140 112 0 61.2 63 168 112 0 −61.2 64 196 112 0 61.2 65 224 112 0 −61.2 66 252 112 0 61.2 67 280 112 0 −61.2 68 308 112 0 61.2 69 336 112 0 −61.2 70 364 112 0 61.2 71 0 140 0 −54 72 28 140 0 54 73 56 140 0 −54 74 84 140 0 54 75 112 140 0 −54 76 140 140 0 54 77 168 140 0 −54 78 196 140 0 54 79 224 140 0 −54 80 252 140 0 54 81 280 140 0 −54 82 308 140 0 54 83 336 140 0 −54 84 364 140 0 54 85 0 168 0 −46.8 86 28 168 0 46.8 87 56 168 0 −46.8 88 84 168 0 46.8 89 112 168 0 −46.8 90 140 168 0 46.8 91 168 168 0 −46.8 92 196 168 0 46.8 93 224 168 0 −46.8 94 252 168 0 46.8 95 280 168 0 −46.8 96 308 168 0 46.8 97 336 168 0 −46.8 98 364 168 0 46.8 99 0 196 0 −39.6 100 28 196 0 39.6 101 56 196 0 −39.6 102 84 196 0 39.6 103 112 196 0 −39.6 104 140 196 0 39.6 105 168 196 0 −39.6 106 196 196 0 39.6 107 224 196 0 −39.6 108 252 196 0 39.6 109 280 196 0 −39.6 110 308 196 0 39.6 111 336 196 0 −39.6 112 364 196 0 39.6 113 0 224 0 −32.4 114 28 224 0 32.4 115 56 224 0 −32.4 116 84 224 0 32.4 117 112 224 0 −32.4 118 140 224 0 32.4 119 168 224 0 −32.4 120 196 224 0 32.4 121 224 224 0 −32.4 122 252 224 0 32.4 123 280 224 0 −32.4 124 308 224 0 32.4 125 336 224 0 −32.4 126 364 224 0 32.4 127 0 252 0 −25.2 128 28 252 0 25.2 129 56 252 0 −25.2 130 84 252 0 25.2 131 112 252 0 −25.2 132 140 252 0 25.2 133 168 252 0 −25.2 134 196 252 0 25.2 135 224 252 0 −25.2 136 252 252 0 25.2 137 280 252 0 −25.2 138 308 252 0 25.2 139 336 252 0 −25.2 140 364 252 0 25.2 141 0 280 0 −18 142 28 280 0 18 143 56 280 0 −18 144 84 280 0 18 145 112 280 0 −18 146 140 280 0 18 147 168 280 0 −18 148 196 280 0 18 149 224 280 0 −18 150 252 280 0 18 151 280 280 0 −18 152 308 280 0 18 153 336 280 0 −18 154 364 280 0 18 155 0 308 0 −10.8 156 28 308 0 10.8 157 56 308 0 −10.8 158 84 308 0 10.8 159 112 308 0 −10.8 160 140 308 0 10.8 161 168 308 0 −10.8 162 196 308 0 10.8 163 224 308 0 −10.8 164 252 308 0 10.8 165 280 308 0 −10.8 166 308 308 0 10.8 167 336 308 0 −10.8 168 364 308 0 10.8 169 0 336 0 −3.6 170 28 336 0 3.6 171 56 336 0 −3.6 172 84 336 0 3.6 173 112 336 0 −3.6 174 140 336 0 3.6 175 168 336 0 −3.6 176 196 336 0 3.6 177 224 336 0 −3.6 178 252 336 0 3.6 179 280 336 0 −3.6 180 308 336 0 3.6 181 336 336 0 −3.6 182 364 336 0 3.6

E. Exemplary Apparatus—Refractive Lens

Optical refractive lenses 60, or TIR lenses 50, FIG. 1C, could be placed over the LED light sources to distribute the light, creating a similar effect, i.e. a highly controlled and customizable composite beam from a light fixture(s) with a plurality of light sources. The lenses can be made of various materials depending on application, cost considerations, availability, etc. For example, the lens could be made of molded plastic, optical glass, etc.

F. Exemplary Apparatus—Visor Strips

In embodiments of the present invention, visor strips as shown in FIGS. 8A-C and are installed in order to limit the angle of emittance from the fixture. FIG. 7a illustrates representative light rays 760a-c, 770a-c, and 780a-c emanating from light source 711a-c in a simplified fixture 710 according to aspects of the invention. In FIG. 11A, exemplary rays 170 and 180 (composed of multiple rays 770a-n and 780a-n as represented in FIG. 7a) emanating from light fixture 110 are at an undesirable angle such that instead of illuminating tennis court 140, FIG. 11A-B, they continue in an undesired direction 130. Installing visor 790 as in FIG. 7b blocks all rays 770 and 780 as desired, but also blocks ray 760c from LED 711c. Installing visor 790 as in FIG. 7c does allows transmission of rays 760a-c as desired, but also allows transmission of rays 770a-b and 780a-b, which is not desired. An optional solution according to embodiments of the present invention is shown in FIG. 7d. In the embodiment shown in FIG. 7d, installing identical visor strips 797a-c allow rays 760a-c to be transmitted as desired, and blocks the respective rays 770a-c and 780a-c from their undesired paths and redirects them to provide useable light in the target area.

These visor strips are shown in use with reflective optics, however the strips can be used with refractive or other optics in embodiments of the present invention.

The visor strips could be constructed of metal, plastic, or other materials. They can be coated with various materials to provide any type of surface desired, such as specular, diffuse, or light absorbing. The size (i.e. height), placement and angle of the visor strips could be calculated in order to provide specific benefits, such as (a) blocking light at a certain angle relative to the fixture, (b) reflecting light down as seen in FIG. 7D in order to provide additional light in a given area (e.g. directly below/in front of a mounting pole/structure). The edges of the visor strips could be linear or could be shaped or modified to provide specific light diffusion characteristics. Optionally, instead of having planar surfaces, the visor strips could be given shapes that would provide further benefits for control or distribution of light in embodiments of the present invention.

The visor strips 797 could be mounted (a) in a standard configuration per fixture, (b) could be designed and mounted at a specific angle or location according to a custom or semi-custom fixture configuration, or (c) could be adjustable by the installer or user. The mounting angle and height of the visor strips 797, FIG. 7D, relative to the fixture could be adjusted in the factory or field. For example, in embodiments of the present invention the fixtures could be adjusted by either a mechanism that provides variable tilt, or by installation of visor strips with a mounting angle that could be specified, or by other means. Mounting height could be adjusted by shims, selection of different height visors per application, threaded adjustment, or other means.

G. Exemplary Apparatus—Light Blocking Tabs

An additional optional feature is a protruding tab 35 FIG. 9 in the vicinity of the light source which is used to block and/or reflect light which is directly emitted by the light source rather than being reflected from the reflector. The tab could be made of material which would block or reflect light, and could be more or less specular, diffusing, and/or absorbing, depending on the desired effect, position relative to the source, etc.

H. Exemplary Apparatus—Combination of Lens Types

In accordance with embodiments of the present invention, the individual optic combinations in the fixture can include a mix of refractive lenses and reflectors and may also include reflective tabs or visor strips.

I. Apparatus—Exemplary, Not Limiting

The components described above are meant to exemplify some types of possibilities. In no way should the aforementioned examples limit the scope of the invention, as they are only exemplary embodiments.

In conclusion, as illustrated through the exemplary embodiments, the present invention provides novel systems, methods and arrangements for deriving composite beams from LED or other lighting. While detailed descriptions of one or more embodiments of the invention have been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art without varying from the spirit of the invention. Therefore, the above description should not be taken as limiting the scope of the invention.

Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations thereof.

Claims

1. A lighting fixture for producing an adjustable, coordinated, relatively high intensity light output for application to a relatively large target area comprising:

a. a housing;

b. a mounting interface in the housing;

c. a plurality of individual lighting elements mounted to the mounting interface in the housing, each lighting element comprising a solid state light source and an associated optic which together produce a light output of customizable characteristics, the associated optic independently adjustable in position or orientation relative its said solid state light source;

d. at least two lighting elements configured to produce light outputs of different characteristics related at least to position or orientation of the said optics.

2. The lighting fixture of claim 1 wherein the solid state light source comprises an LED.

3. The lighting fixture of claim 1 wherein the optic comprises one or more of refractive or reflective components.

4. The lighting fixture of claim 3 wherein the optic which produces a directional light output depending on adjustable orientation to the light source.

5. The lighting fixture of claim 1 wherein the mounting interface comprises an alignment plate with pre-designed receivers to position and orient the optic for each lighting element.

6. The lighting fixture of claim 5 further comprising a plurality of alignment plates for each fixture, so that different coordinated light outputs from the fixture are at least in part a function of the selection of alignment plate.

7. The lighting fixture of claim 1 wherein the light output characteristic of each lighting element can be adjusted as to one or more of shape, size, intensity, or distribution.

8. The lighting fixture of claim 1 wherein the light output of the fixture is uniform at the target area but is non-uniform at the fixture.

9. The lighting fixture of claim 1 wherein the light output of the fixture is adapted to compensate for inverse square law or for cosine correction.

10. A lighting system comprising:

a. a plurality of lighting fixtures of claim 1.

11. A method of lighting a relatively large target area with a lighting fixture comprising:

a. determining a desired light output pattern and distribution at the target area;

b. coordinating and configuring a plurality of individual solid state light sources and associated optics to produce the desired light output pattern at the target area, the associated optic independently adjustable in at least position or orientation relative its said solid state light source.

12. The method of claim 11 wherein each associated optic has at least one adjustable feature related to changing the light output characteristic of the associated solid state light source.

13. The method of claim 12 wherein the adjustable feature comprises optic type and characteristics, optic shape, optic orientation.

14. The method of claim 11 wherein the solid state light sources comprise LEDs.

15. The method of claim 11 wherein the desired light output pattern and distribution is customized for a given target area.

16. The method of claim 15 wherein the customized light output is from a single fixture housing the plurality of solid state light sources and associated optics.

17. The method of claim 15 wherein the customized light output is from plural fixtures each housing a subset of the plurality of solid state light sources and associated optics.

18. The method of claim 17 wherein the plural fixtures are coordinated to produce a composite illumination of the target area.

19. The method of claim 15 wherein the customization is based on an analysis and selection of various output patterns and distributions possible from each light source and optic.

20. The method of claim 19 further comprising providing an inventory of varying light sources and optics for selection of lighting elements.

21. The method of claim 20 further comprising an inventory of mounting interfaces for the optics relative to a fixture housing, each mounting interface comprising an alignment plate for mounting a plurality of optics in varying orientations to produce varying coordinated light outputs.